Incremental deflection of cathoderay beam



Feb. 2- 2, 1948. R. a... SNYDER, JR

INCREMENTAL DEFLECTION OF CATHODE RAY BEAMS Filed De 25 INPUT? 2%Clttorneg I Patented Feb. 24, .1948- UNITED STATES ATENT OFFICEINCREMENTAL .DEFLECTION F CATHODE- RAY BEAM Richard L. Snyder, Jr.,Princeton, N. J assignor to Radio Corporation of America, a corporationof Delaware 7 Claims.

This invention relates generally to electronic computers andparticularly to an improved method of and means for obtainingincremental 'defiection of a cathode ray beam in response to appliedvoltage pulses.

The instant invention is an improvement on applicant's copending U. S.application, Serial No. 455,420, filed August 20, 1942, now abandonedand the copending U. S. application of George A. Morton and Leslie E.Flory, Serial No. 456,012, filed August 25, 1942, which both discloseelectronic computing devices employing incremental cathode raydeflection in response to applied voltage pulses. The present invention,however, includes additional advantages and improvements over thecopending applications, mentioned heretofore, in that it providescathode ray deflection of on1y.0ne increment in response to applieddeflection voltage pulses of any amplitude which exceeds a predeterminedminimum value. In addition, the direction of the cathode ray deflectionis determined by the polarity of the deflecting pulses, whereby thetotal deflection is proportional to the algebraic sum of the number ofapplied positive and negative deflecting voltage pulses.

Briefly, the invention employs the general type of feedback circuit,disclosed in the copending Morton and Flory application, for positioningthe electron beam to impinge upon the edge of a target electrode aftereach beam deflection. However, an improved circuit is provided fordetermining the direction of the beam deflection by the polarity of theapplied deflection pulses, and for limiting the beam deflection to asingle increment in response to each deflection pulse.

The first embodiment of the invention, to be described hereinafter,employs a cathode ray tube having conventional ray generating and raydeflecting means. A plurality of target electrodes, preferably disposedon a common arc having its center on the beam axis, are spacedpredetermined distances from each other. Alternate electrodes areconnected together electrically. One group of electrodes is connected toone control electrode circuit of a balanced amplifier, and the remaininggroup of electrodes is connected symmetrically to another controlelectrode circuit of the amplifier. The balanced output circuit of theamplifier is connected symmetrically to the deflecting elements of thecathode ray tube. Pulses are applied to the amplifier input circuit insuch a manner that the pulse polarity determines the direction ofcathode ray deflection. The feedback circuit through the amplifierfromthe target electrodes to the deflection means accurately positionsthe cathode ray after each pulse deflection thereof.

The second embodiment of the invention employs a similar cathode raytube and a balanced amplifier but includes separate deflection circuitswhich employ trigger circuits responsive to the applied pulses. A firsttrigger circuit is responsive only to positive applied pulses. A secondtrigger circuit is responsive only to negative ape plied pulses, while athird trigger circuit is responsive to actuation of either the first orthe second trigger circuits. The first trigger circuit deflects thecathode ray beam one increment in one direction. The second triggercircuit. deflects the cathode ray beam one increment in the oppositedirection. The third trigger circuit reverses the sense of the balancedamplifier with each applied input pulse, whereby the feedback deflectioncontrol voltages are always of the proper polarity to position thecathode ray beam after each incremental deflection thereof. Since theapplied Voltage pulses only actuate either the first or the secondtrigger circuits, the cathode ray deflection isindependent of theamplitude of the pulses,

providing they exceed the minimum value necessary to actuate the triggercircuits.

Among the objects of the invention are to provide an improved method ofand means for obtaining incremental deflection of a cathode ray beam;Another object is to provide an improved method of and means forcounting voltage pulses. Another object is'to provide an improved methodof and means for obtaining unitary incremental deflection of a cathoderay beam in response to applied voltage pulses of any amplitude whichexceeds a predetermined minimum value. Still another object is toprovide an improved method of and means for obtaining unitaryincremental deflection of a cathode ray beam in response to appliedvoltage pulses which exceed a predetermined amplitude wherein thepolarity of said pulses determines the direction of the cathode ra beamdeflection.

The invention will be described in detail by reference to theaccompanying drawing of which Figure 1 is a schematic circuit diagram ofone embodiment thereof; and Figure 2 is'a schematic circuit diagram of asecond and preferred "enibodiment thereof. Similar reference numeralsare applied to similar elements throughout the drawing.

Referring to Figure 1, a. cathode ray tube 1 includes a cathode 2, acontrol electrode 3, a screen electrode 4, and an anode 5 which aresupplied with operating voltages from a voltage divider 6. A source ofhigh potential is connected across the voltage divider 6. A resistor Iis connected between the control electrode 3 and the negative terminalof the voltage divider 6. The tube I includes deflecting elements 8, 8which are disposed adjacent the axis of the cathode ray between theanode 5 and a plurality of target electrodes 9, Ill, H, l2, l3 and M.The target electrodes 9, I0, I i, i2, i3 and M are preferably juxtaposedforming an arc'having its center on the axis of the cathode ray beamadjacent the anode 5, and intersecting the plane of the deflectedcathode ray beam.

Alternate target electrodes 9, H and I3 are connected together andthence connected to the control electrode of a first amplifier tube I5of a balanced amplifier ll. Similarly, the remaining target electrodesm, l2 and 14 are connected together and thence connected to the controlelectrode of a second amplifier tube It; of the balanced amplifier H. Afirst capacitor [8 is connected from the target electrodes 9, ll, l3 toground. A second capacitor i9 is connected from the, target electrodesl0, 12, Hi to ground.

The cathodes of the amplifier tubes l5 and 16 are connected togetherthrough resistors 20, 20' which are connected together and grounded attheir junction. A first grid resistor 2| is connected from the controlelectrode of the first amplifier tube IE to ground. A second gridresistor 22 is connected from the control electrode of the secondamplifier tube 16 to ground. Anode potential from any suitable voltagesource is applied to the anodes of the amplifier tubes l5, [B throughresistors 23, 24, respectively. The negative terminal of the anodevoltage source is connected to ground. The anode of the first amplifiertube [5 is connected to the cathode beam deflecting element 8, while theanode of the second amplifier tube [6 is connected to the beamdeflecting element 8'. Input deflection pulses may be applied to theamplifier cathode circuit across the grounded cathode resistor 20, towhich the input terminals 25, 26 are connected. The

input pulses preferably should be shaped to provide a sawtooth waveformwhich rises rapidly and diminishes slowly.

The amplifier deflection pulses will thence be applied to the deflectionelements 8, 8' to deflect the beam in a direction dependent upon thepolarity of the applied pulses. The capacitors l8 and I9 should beselected to have a charging time sufflcient to permit the desireddeflection increments on the rising part of the pulse before thefeedback system can operate. These capacitors should be small enough toallow the feedback system to hold the beam in its new position while thepulse voltage is slowly diminishing.

As pointed out above, the input pulses should be shaped to provide asawtooth wave which rises rapidly and falls slowly. When such a pulse isof negative polarity and is applied to the input terminals 25-26, thecurrent of tube 15 and the resistor 23 is reduced, the deflectingelectrode 8 becomes more positive and the beam moves from the boundarybetween the target members II and [2 to that between the members l3 andIt. During this movement, the target voltage is essentially unchangedbecause capacitors l8 and 19 cannot be charged by the current in thebeam during its transit across the target members I2 and [3. This is sobecause the amount of charge delivered to the capacitors I8 4 and I9 bythe electrons in the beam during the transit period is very smallcompared to the charge necessary to produce an appreciable voltagechange across these capacitors.

The voltage of the pulse falls from its maximum value at a fairlyuniform rate and reaches zero in a time which is much greater than thatrequired for its rise. During this relatively slow decrease in voltage,the electron beam starts to move from the boundary between the targetmembers l3 and I4 onto the member l3. As this movement is relativelyslow, the beam current to the member 13 has time to charge the capacitor18 negative and the lowering of the current to the member I4 andcapacitor I9 continues for suflicient time to allow the charge ofcapacitor [9 to become less negative. These voltage changes of thecapacitors l8 and I9, which are connected to the grids of the tubes [5and i6, thus change in such a way as to reestablish the beam at theboundary between the members 13 and M where it is stabilized by reasonof the fact that the beam is divided between these two members. Underthese conditions, the currents of the tubes l5 are balanced and furthermovement of the beam requires the application of an additional pulse tothe input terminals 25-26.

If this additional pulse be positively polarized, the current of thetube [5 and resistor 23 is increased, the polarity of the deflectingelectrode 8 becomes more negative and the electron beam is moved fromthe boundary between I3 and M to the boundary between H and 12. Duringthis movement, the target voltage is essentially unchanged, as pointedout above. As the applied pulse voltage slowly falls to zero, the beamstarts to move from the boundary line between the members I! and I2 ontothe member i2, the charge of the capacitor 19 tends to become morenegative and that of the capacitor i 8 tends to become less negative,the current of the tube l6 tends to decrease and that of the tube l5tends to increase, and the beam is stabilized at the boundary betweenthe members It and I2, as previously explained.

The application of a further positive pulse results in movement of thebeam to the boundary line between the target members 9 and ID, where ittends to move onto the segment It), thus making the charge of thecapacitor l9 more negative and that of the capacitor l8 less negative,and stabilizing the beam at the boundary line between the members 9 and10.

As previously indicated, the target members are insulated and spacedfrom one another. A construction found satisfactory was the arrangementof the members in the form of a partly opened Venetian blind so that theopposed edges of the members overlapped without touching one another.

The arrangement of Fig. 2 differs from that of Fig. 1 in that thepositive and negative pulses are applied to diiferent trigger circuitsof the slideback type and the electron beam is stabilized at everytarget boundary instead of every other target boundary, as in the caseof Fig. l where both the positive and negative pulses are applied to thesame terminals. In other respects, the operation of the embodiments ofFigs. 1 and 2 is similar.

Referring to Figure 2, the cathode ray tube is connected similarly tothe tube of Fig. 1 with the exception of the target electrode groups andthe beam deflection elements. Input pulses applied to the terminals 25,25 are impressed upon two trigger circuits 21, 28. These triggercircuits are of the slideback type described in the copendingapplication of George A. Morton and Leslie E. Flory, Serial No. 473,146,filed January 21,1943, now Patent No. 2,404,047, granted July 16, 1946.The trigger circuit 21 includes a first trigger tube '29 and a secondtrigger tube 30, which is normally non-conducting. The trigger circuit28 includes a first trigger tube 3|, which is-norm'ally non-conductive,and a second trigger tube 32 which is normally conductive. Input pulsesare applied to the grid of the first trigger tube 29 of trigger circuitii, and to the grid of the first trigger tube .H of trigger circuit 28.Thus negative pulses applied to the input terminals 25, 28 willtemporarily recondition the trigger circuit 27, while positive pulseswill temporarily recondition the trigger circuit 28. A negative inputpulse of any amplitude which exceeds some predetermined minimum valuewill therefore produce a positive pulse in the anode circuit of thefirst trigger tube 29 of trigger circuit 21. This positive pulse isapplied, through a first capacitor 35, to the control electrode circuitof a first triode of a diode-triode 33, from which is derived a negativepulse which is applied tothe cathode ray tube deflecting element 8 todeflect the cathode beam upward a predetermlned vertical incrementdetermined only by the circuit constants Similarly, a positive pulseapplied to the input terminals 25, 26 will produce a positive pulse inthe anode circuit of the second trigger tube 32 of the second triggercircuit 28. This positive pulse is applied, through a second capacitor36, to the control electrode of a second triode of a second diode-triode34, from which is derived a negative pulse which is applied to thecathode ray tube deflecting element 8 to deflect the beam downward thepredetermined increment determined only by the circuit constants.

The anodes of the trigger tubes 3i) and M are connected, respectively,through third and fourth capacitor 37 and 38 to the symmetrical point 39of the anode circuits of a third trigger circuit 48, including first andsecond trig er tubes 4|, "42', which is of the conventional type alsodescribed in the Morton and Flory patent, mentioned heretofore. Inputpulses of either polarity will provide negative pulses at the point 38to effect a change in polarization of the third trigger circuit 4H.

A balanced amplifier 47, includes four pentagrid tubes 43, 44, 45, 46.The cathodes and suppressor grids of the pentagrid tubes 43 and 44 areall connected to ground through a first cathode resistor 48. Thecathodes and suppressor grids of the pentagrid tubes 45 and 46 aresimilarly connected to ground through a second cathode resistor 49. Thescreen and anode electrodes of all four pentagrid tubes are suppliedwith operating voltage through a network which includes the resistors50, 5!. The anodes of the tubes 43 and 45 are connected to the cathoderay deflecting element 8. The anodes of the tubes 44 and 46 areconnected to the cathode ray deflecting element 8'.

The target electrode 9, H and [3 are connected together, and connectedto the second control electrodes of the pentagrid tubes 44 and 45. Agrid resistor 52 is connected from these grids to ground. Similarly thetarget electrodes l0, l2 and I4 areconnected together, and connected tothe second control electrodes of the pentagrid tubes 43 and 46. A secondgrid resistor 53 is 6 connected from the-last: mentioned griusto ground.

The first control grids of the pentagrid-tubes 43 and 44 are connectedto the grid of the first trigger tube 4| of the third trigger circuit'49. Similarly the first control'grids of the pentagrid tubes 45 and 46are connected to the grid of the second trigger tube 42 of "the thirdtrigger circuit 40. It will therefore be seen that the balancedamplifier 41 provides a feedback deflection control circuit for thecathode ray tube I, and that the sense of the amplifier 41- is changedby each impulse to effect a balance of the beam on the next boundarybetween target electrodes.

It should be understood that the invention lends itself to both magneticand electrostatic types of cathode ray'deflection, and that either maybe employed.

The anodes of the diode portions of the first and second diode-tr'iodes33 and 34 are connected to ground. The cathodes 'of each of thediode-triodes are connected together and to a source of negative biaspotential throughseparate cathode bias resistors 54, 55, respectively.This arrangement insures that the current drawn by the triode will beindependent of the tube characteristics, so that the'charge delivered toeither capacitor 56 or 5'! during a deflection pulse depends only on theduration of the pulse. The duration of the pulse is determined by theconstants of the capacitors 36 and 35in conjunction with the constantsof their respective cooperating resistors 58 and 59 which-are connectedtogether, and connected through a ca pacitor-resistance network 50, Stto ground.

Deflection capacitors 56,51 are connected between the deflectionelements 8, 8", respectively, and ground, to insure that the deflectionincrement inresponse to the input pulses is completed; before thedeflection feedback voltages from the balanced amplifier 4'? takeeffect, to position the cathode ray beam on the corresponding targetelectrode.

Thus the invention described comprises improved methods of and means fordeflecting a cathode beam in discrete steps in a direction determined bythe polarity of applied voltage pulses, wherein the deflection incrementis substantially independent of the amplitudes of the applied voltagepulses.

I claim as my invention:

1. A cathode ray tube circuit for counting voltage pulses including acathode ray tube having ray generating means, ray deflecting means, anda plurality of target electrodes, means connecting alternate targetelectrodes in separate parallel groups, means including a balancedamplifier for applying said pulses to said ray deflecting means todeflect said ray across said target electrodes, means including saidtarget electrodes and said amplifier for accurately positioning said raywith respect to the next adjacent one of said target electrodes aftereach application of one of said pulses to said deflecting means, andmeans for controlling the direction of said deflection in accordancewith the polarity of each of said pulses,

2. A cathode ray tube circuit for deflecting a cathode ra in singlediscrete steps and a direction corresponding to the polarity of appliedvoltage pulses including a cathode ray tube having ray generating means,ray deflecting means, and a plurality of target electrodes, meansconnecting alternate target electrodes in parallel relation, a pair ofbalanced amplifiers, means for applying said pulses symmetrically tosaid amplifier, means connecting each group of said target electrodes toa difierent one of said amplifiers, and means connecting said amplifiersto difierent ones of said deflecting means for applying said pulsesthereto to deflect said ray across said target electrodes.

3. A cathode ray tube circuit for deflecting a cathode ray in singlediscrete steps in a direction corresponding to the polarity of appliedvoltage pulses including a cathode ray tube having ray generating means,ray deflecting means, and a plurality of target electrodes, meansconnecting alternate target electrodes in parallel relation, a balancedamplifier, means including a pair of trigger circuits for selectivelyapplying said pulses to said deflecting elements, means connecting eachgroup of said target electrodes to diflerent tubes of said amplifier,and means connecting said amplifier to said deflecting means to providea feed-back circuit to deflect said ray across said target electrodes.

4. A cathode ray tube circuit for deflecting a cathode ray in singlediscrete steps in a direction corresponding to the polarity of appliedvoltage pulses including a cathode ray tube having ray generating means,ray deflecting means, and a plurality of target electrodes, meansconnecting alternate target electrodes in parallel relation, a balancedamplifier, means including a pair of trigger circuits for selectivelyapplying said pulses to said deflecting elements, means including athird trigger circuit for selectively applying said pulses to difierenttubes of said amplifier, means connecting each group of said targetelectrodes to different tubes of said amplifier, and means connectingsaid amplifier to said deflecting means to provide a feedback circuit todeflect said ray across said target electrodes.

5. A cathode ray tube circuit for deflecting a cathode ray in singlediscrete steps in a direction corresponding to the polarity of appliedvoltage pulses including a cathode ray tube having ray generating means,ray deflecting means, and a plurality of target electrodes, meansconnecting alternate target electrodes in parallel relation, a balancedamplifier, means including a pair of trigger circuits and a pair ofdiode-triodes for selectively applying said pulses to said deflectingelements, means including a third trigger circuit for selectivelyapplying said pulses to different tubes of said amplifier, meansconnecting each group of said target electrodes to difi'erent tubes ofsaid amplifier, and means connecting said amplifier to said deflectingmeans to provide a feedback circuit to deflect said ray across saidtarget electrodes.

6. Apparatus of the type described in claim 5 including a pair ofcapacitors, a source of reference potential, and means connecting eachof said deflecting means through one of said capacitors to said sourceof reference potential.

7. A cathode ray tube circuit for deflectinga cathode ray in singlediscrete steps in a direction corresponding to the polarity of appliedvoltage pulses including a cathode ray tube having ray generating means,ray deflecting means, and a plurality of target electrodes, meansconnecting alternate target electrodes in parallel relation, a balancedamplifier including parallel push-pull connected pentagrid tubes, meansincluding a pair of trigger circuits for selectively applying saidpulses to said deflecting elements, means including a third triggercircuit for selectively applying said pulses to different tubes of saidamplifier, means connecting each group of said target electrodes todifierent tubes of said amplifler, and means connecting said amplifierto said deflecting means to provide a feedback circuit to deflect saidray across said target electrodes.

RICHARD L. SNYDER, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

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